Ringing control circuit



Dec. 26, 1950 Filed Oct. 29, 1948 02/6. OFFICE TRAFFIC I 4 PEGCCZ'PEG/5m? LINK M. C- GODDARD RINGING CONTROL CIRCUIT MA E/(EE 2Sheets-Sheet 1 60 0? I20 [PM INT C67.

INVENTOI? Mc Goon/m0 ATTORNEY Patented Dec. 26, 1950 UNITED STATESPATENT OFFICE RINGING CONTROL CIRCUIT Myron C. Goddard, Garden City, N.Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N.Y., a corporation of New York Application October 29, 1948, Serial No.57,386

9 Claims.

This invention relates to telephone systems in In a system of this typea marker is employed to control the operation of cross bar switcheslocated on a line link frame and on a trunk link frame to select an idlechannel extending from a desired subscribers line to one end of an idleintra office trunk circuit which terminates at both of its ends atcross-points of cross bar switches on the trunk link frame if the callis to be terminated in the originating ofilce. This selected channel isset up in accordance with the digits of the desired line number dialedby the calling subscriber. When such channel is selected and the markerfinds the desired line to be idle, the marker then selects an idlechannel extending from the calling line to the other end of theintra-ofiice trunk circuit and operates cross bar switches on the linelink frame on which the calling line terminates and on the trunk linkframe on which the selected intraoflice trunk circuit terminates inaccordance with the selected channel to interconnect the calling andcalled lines.

Revertive calls to a called station from a calling station on the sameline are made in a manner similar to an intra-ofiice call except that arevertive call trunk is selected rather than an intra-office trunkcircuit. a

Calls from subscribers lines terminating in distant offices fortermination in a cross bar office of the type just described, enter suchoflice over an incoming trunk circuit which terminates at a cross-pointof a cross bar switch on a trunk link frame. When such incoming trunkcircuit is seized an incoming register is associated therewith over aregister link to receive the digit information necessary to enable themarker of the terminating oflice to control cross bar switches on thetrunk link frame on which the incoming trunk circuit terminates andswitches on the line link frame on which the desired or called lineterminates to complete the connection from the incoming trunk circuit tothe desired line. i

In terminating a local call in a cross bar oflice which is establishedover an intra-offilce trunk circuit or revertive call trunk circuit orfor a call from a distant ofiice over an incoming trunk circuit, it isnecessary to supply ringing current to the station of the called line inaccordance with the type of line on which the called station is located.The line may be of the individual type, may be a two-party, a four-partysemiselective, a four-party full selective, an eightpartysemi-selective, or a ten-party five-code line. Also, it is necessary oncalls incoming from a distant ofiice to inform the calling subscriber inthe distant oiflce if the called line is busy or if an all-paths-busycondition is encountered at the terminating ofiice by the marker whenattempting to select an idle channel over which a connection may beestablished from the incoming trunk circuit to the desired line.

It is the object of the present invention to provide equipment common toa plurality of trunk circuits of either the intra-oflice, revertive callor incoming type which may be selectively controlled by the marker toapply the required type of ringing signal to a called line or to causethe transmission of a busy signal to the calling line On acalled-line-busy or allpaths-busy condition.

In accordance with the present invention this object is attained by theprovision of a ringing selection switch circuit comprising a cross barswitch, which circuit is common to a group of trunks. The verticals ofthe switch are allocated to the several trunk circuits to which thecircuit is common and the select magnets are selectively operable by amarker. Seven of the select magnets are selectively operable todetermine the type of ringing signal to be applied to a trunk circuit,two of the select magnets are selectively operable to determine whetherthe ringing signal is to be applied to the tip or ring accepts'scription when read in connection with the drawing in which:

Fig. 1 shows a trunk circuit incoming from a distant ofiice, theschematic representation of a calling line and originating ofiice inwhich such line terminates and the schematic representation of anincoming register, an incoming register link by which the register isassociated with any one of a plurality of incoming trunk circuits, and amarker connector by which the incoming register is associated with anidle marker of the terminating oince; and

Fig. 2 shows schematically a marker, a number a group circuit, numbergroup connector, trunk link frame, trunk link connector, line linkframe, line link connector and called line at the terminating office,and a ringing selection switch circuit in accordance with the presentinvention common to a group of trunk circuits, one of which trunkcircuits is disclosed in Fig. 1.

For a complete discloseure of the invention, Fig. 2 should be placed tothe right of Fig. 1.

The switches schematically disclosed in the boxes of Fig. 2 labeledTrunk Link Frame and Line Link Frame and the ringing selection switch ofFig. 2 are of the well-known cross bar type such as is disclosed forexample in Patent 2,021,329, granted November 19, 1935, to J. N.Reynolds.

The circuits and apparatus schematically disclosed in Figs; 1 and 2 arefully dis-closed and described in the application of A. J. Buschhereinbefore referred to and such portions of said ap-.

plication-as are of assistance in the comprehen sion of the presentinvention are to be considered as embodied in the disclosure of thisapplication.

An intra-oflice trunk circuit of the type served by the ringingselection switch circuit of Fig. 2

is disclosed in the ccpending application of L. T.

Anderson. and M.. C. Goddard, Serial No. 57,387, now Patent No.2,599,050, granted May 23, 1950, a

revertive call trunk circuit of the type served by the ringing selectionswitch circuit is disclosed in the copending application of R. E.Hersey, Serial No. 57,397, filed October 29, 1948.

The invention will now be considered in detail. It will be assumed thatthe .calling station designated its in Fi 1 whose lin for xampl trunkswitch in the trunk link frame Elli of the terminating office.

When this trunk circuit is seized by the A relay I03 of the trunkcircuit is operated in a circuit which may be traced in part frombattery'through the right winding of relay 503, the left No. 3 backcontact of the CO relay I04, over the tip conductor 505 of theinter-office trunk, thence over the trunk loop, returning over the ringconductor I06, the left No. 4 back contact of relay E04 and through theleft winding of relay I03 to ground. Relay I03 operates over thiscircuit and connects battery through resistor 907, over the lower backcontact of the trunk reversal (T) relay tilt, the right No. 2 backcontaft of the CO relay I04, the

' contacts for relay 903, the right No. 3 back contact of relay I04, andto the ST lead extending to the e incoming register link circuit I08. Ifan incom ing register is available, the register link switch operates toconnect the idle register with the trunk circuit at which time theregister takes control of the start lead ST and operates the CO relayI04 of the trunk circuit. It will be assumed that the incomingregisterN39 is idle and is instrumental in connecting ground to the CO leadthereby causing the operation of the CO relay 104 of the trunk circuit.

Relay i0 3 upon operating disconnects the windings of the A relay m3from the conductors I05 and 608 of the inter-ofiice trunk circuit M3 atits Nos. 3 and 4 left back contacts to provide a free pulsing path tothe incoming register over the tip and ring leads T and R extendingthrough the register link I00 to the reister W9, and prepares over itsNos. 2 and 3 right front contacts and the contacts of the A relay Hit, alocking circuit for the D relay H0. Relay I04 also connects ground overits left No. 1 contacts to lead BL eX- tending to the register I09 as acheck of its operation.

When pulsing is completed, the register I09 connects ground to lead Dthereby causing the operation of the D relay' H0. Relay H0 uponoperating connects the right winding of the A relay 103 over its upperNo. 3 contacts and the upper back contact of the T relay I03 to the tipconductor 505 of the trunk circuit and cone nects the left winding ofrelay 593 over the lower No. 4 contacts of relay I I0 and the innerlower back contact of relay N38 to the ring conductor 105 of the trunkcircuit I43 whereupon relay. I03 reoperates and establishes the lockingcircuit for the D relay IIO which locking circuit may be traced frombattery through the winding of relay Ii0, over the No. 3 right frontcontact of the CO relay I04, over the contacts of relay I03, the No. 2right front contact of relay i0 1 and to ground over the lower No. 2contacts of relay I I0. Transmission current for the inter-oiiice trunkis supplied through the windings of the A relay I03. Relay H0 alsoconnects ground through the 10- c-hm resistor III, over its upper No. 1contacts to the sleeve conductor H2 or the trunk appearance on the trunklink frame 205 for holding the trunk link and line link switches afterthe trunk link frame (F) relay li3 releases, and connects ground overits lower No. 1 and No. 3 contacts erated.

The incoming register following its seizure becomes connected tO, anidle marker through the marker connector II4. It will be assumed thatthe marker schematically disclosed in the dotdash rectangle 202 of Fig.2 is available and is seized. The marker reaches the trunk circuitthrough the marker connector I I4, incoming register I09 and registerlink I08 and connects ground to the F lead thereby causing the operationof the F relay I I3. Relay I I3 upon operating connects ground to the FAlead I i5 thereby causing the operation of relay 203 in the trunk linkconnector 204; closes the TC lead 205 from the trunk link connector,over its No. 3 left contacts and through the winding of the TC relay H6and to battery; closes the RC lead 206 from the trunk link connector204, over its No. 1 right contacts to the winding of the RC relay II!and to battery; closes the circuit of the peg count register in thetrafiic register circuit I44 and at its right No. 2 transfer contactstransfers the control of the ringing selection switch hold magire'tzsl-tve'mhe TP lead 201 to the trunk link connector 204. l

When the relay 203 of the trunk link connector 204 operates underthecontrol of the trunk circuit, it prepares the circuit for operating theselectmagnet of the trunk link frame 20I corre-- sponding to the levelof the trunk switch in which the incoming trunk circuit has itsappearance and causes theoperation of the level (LV) relay 208corresponding to such level which relay upon operating prepares to cutthrough leadsfrom the trunk link connector, the ringing selectionswitchcircuit and the trunk circuit to the marker. The marker 202 which hasbeen seized having received the numerical digits dialed into theincoming register I09 and the number of the trunk link frame on whichthe incoming trunk circuit ter- 'minates, seizes the trunk link frame byoperating the MCA relay 200 of the trunk link frame connector 204allocated to the trunk link frame 20I whereupon control circuitsprepared by the operation of the LV relay 208 are cut through to themarker.

When the marker seizes the trunk link frame it also seizes through thenumber group connector 2 I the proper number group of the number groupcircuit in accordance with the thousands group of the number dialed intothe incoming register I99 and sets the number group to determine thelocation of the desired line on the line link frame 2 I2. After thecalled line location has been obtained from the number group and thetrunk link frame has been seized, the marker seizes the line link theline link and trunk link frames 2I2 and 20I to establish the channel. Ifthe called line is busy or all channels over which the called line maybe. reached are busy the calling subscriber is given a busy signal inthe manner to be presently described.

The number group also gives the marker information for setting theringing selection switch .250 of Fig. 2 for ringing the calledsubscriber ii the called subscribers line is idle by operating one 'offifteen RCT relays of the marker, three of such relays RCTd, RCTG andRCTI5 being shown and designated 2M, 2I5 and 2H5, respectively. The

incoming trunk circuits appear on verticals of the ringing selectionswitch 250 as indicated by the hold magnets and different code leadsappear in the horizontals. The marker, after receiving therequiredinformation from the number group and after an idle channel has beenselected operates the'selected hold magnet to connect the proper ringinginto the trunk circuit. The marker then disconnects and leaves theringing selection switch 259 held by the trunk circuit.

After the marker has operated the required select magnets of the ringingselection switch 250 over circuits extending through contacts of the:SEleClJBd RCT relay of the marker, contacts of the "MCA relay 209 andcontacts of the LV relay 20d, ground is applied from the marker over acircuit :extending over contacts of relays 209 and 208 to the no lead2116 thereby causing the operation of ates-hi5 the RC relay II! of thetrunk circuit. Relay I I1 thereupon operates and establishes a circuitfrom ground applied at the marker over contacts of relays 209 and 208,the TP lead 201,.the right No. 2 contacts of the F relay II 3, the upperNo. 3 contacts of relay I II, the H lead I I8 and through the winding ofhold magnet 25I. of switch 250. Magnet 25I thereupon operates. In thisconnection it is to be noted that the other nine verticals of the switch250 may be allocated to other incoming trunk circuits, to intra-officetrunk circuits or to revertive call trunk circuits which haveappearances on the same trunk link frame 20L It will be assumed that theRCTt relay 2I5 of the marker has previously caused the operation ofselect magnet 2B6 allocated to the code 1 gen-,- erator lead 28I fornegative superimposed ringing which is to be applied for two secondsfollowed by a four-second silent interval. On the assumption that thecalled line is an individualline, the ltCTG relay 2I5 of the marker alsoestablishes a c1rcuit over contacts of relays 209 and 200 for the selectmagnet 250 indicative of this fact. With select magnet 260 operated andholdlnagnet 25I operated cross-point contacts 210 are closed and a holdcircuit for the RC relay H1 is therefore established from batterythrough the winding and upper No. 1 contacts of relay I H, the backcontact of ringing trip (RT) relay I I9, conductor I20, the lowercontacts of cross-point contacts 210, conductor I2I and to ground overthe lower No. 3 contacts of the D relay H0 This locking ground providesa check to the marker that the RC relay III has operated and crosspointcontacts 01 switch 250 and the back contact of the ringing trip relayIII! are closed.

On a charge call the marker connects ground over the contacts of relays209 and 2081, and over the TC lead 205 for operating the TC relay H6wh1ch, upon operating, locks over its No. 1 right contacts, the No. 4left back contact of the BY relay I22 and to ground over the lower No. 3contactsof the D relay IIO.

When the marker has set up the connection to the called line and hascompleted the necessary tests it releases the F relay I I3 therebyreleasing relay 203 at the trunk link connector and returns 1 thecontrol of the hold magnet 25I of the ringing selection switch 250 tothe trunk circuit. Hold magnet 25I is now maintained operated overconductor II8, the upper No. 3 contacts of the RC relay Ill, the rightNo. 2 normal contacts of relay H3 and to ground over the lower No. 3contacts of the D relay H0. The tip and ring conductors of the trunkcircuit I02 are now extended over the cross-points of switches on thetrunk link frame 20I and line link frame 2I2 to the tip and ringconductors of the called line 250 and the sleeve conductor II2 forholding the established connection to the called line is under thecontrol of the D relay H0. The incoming register I09 {and register linkI08 are also disconnected at this ime.

Relay II3 connects interrupted ground from the pick-up supply lead I23over its No. 3 right back contact, over the No. 3 right back contact ofthe BY relay I22, the lower No. 1 contacts of the RC relay 1, throughthe left normal contacts of pick-up (PU) relay I 24 to the pick-up leadI25 extending to the ringing selection switch 250, and thence over theupper No. 2 contacts of the RC relay N1, the upper No. 2 contacts of theD relay I I0 and through the winding of PU relay I24 to battery.however, when thg call is for a one ring" station, as has been assum'ed,the PU relay I24 is-immediately operated without awaiting the closure ofthe interrupter contacts at the pick-up supply source, over lead I25connected over the lower contacts of operated cross-\point contacts 216and the lower contacts of operated cross-point contacts 2'50 to groundon conductor I2I, as soon as such cross- .points close. Relay I24, uponoperating, locks over the circuit traced from its winding to conductor I25, thence over the left alternate con tacts of relay I28 to groundapplied to conductor I2I over the lower No. 3 contacts of the D relayIIII; clears the lead I25 of interrupted ground from the interrupterlead I23 and connects the selected ringing source to the called line.

Ringing current is now connected to the called line from the ringingcurrent supply 289 over code 1 generator lead 28I, over the uppercontacts of cross-point contacts 216, th RT lead I26, through thewinding of ringing trip (RT) relay H9, the RB lead I27, the next-touppercontacts of cross-point contacts 2'56, the ring conductor I29, the outerright contacts of PU relay I24, the lower No. 2 front contact of the RCrelay II'I, over the ring conductor of the estab lished connection tothe called line 239, thence returning over the tip conductor of theestablished connection, over the upper No. 4 front contact of relay Ill,the inner right contacts of relay I24, tip conductor I 28, thenext-to-lower contacts of cross-point contacts 2?:3 and conductor 288 tothe ringing ground of the ringing supply 280. At th same time ringingcurrent is supplied through condensers I 32 and ISI, back over theestablished connection to the calling subscribers line as an audibleringing tone signal.

If the call is not for a one-ringstation, the pick-up relay does notreceive a direct operating ground over cross-points of the ringingselection switch 250 as just described, but awaits a ground. connectionover the right No. 3 back contact of the F relay II3 to insure thatmachine ringing will not start until the beginning of a ringing code.

Should the call be abandoned before the called subscriber answers, the Arelay I23 releases in turn releasing the D relay III? which in turnreleases the PU relay I25 and the RC relay Hi to restore the trunkcircuit and the associated ringing selection switch circuit.

When the called subscriber answers the increased current flow during theringing or silent period voltage operates the ringing trip (RT) relay H9thereby causing the release of the RC relay II'I. Relay II'I uponreleasing opens the circuit over which ringing current was applied tothe called line and the RT relay IIQ releases. With relay Ill releasedthe upper Winding of the S relay I32 is connected over the upper No. 4back contact of relay II! to the tip conductor of the establishedconnection to the called line are and the lower winding of relay. I32 isconnected over the lower No. 2 back contact of relay ill to the ringconductor of the established connection whereupon relay I32 operates.Relay Ii? at its upper No. 2 contacts opens the locking circuit of thePU relay I20 which releases and at its upper No. 3 contacts opens thecircuit of holding magnet 25! of the ringing selection switch 25?;thereby releasing the vertical of such switch used in conjunction withthe trunk circuit of Fig. 1.

The S relay at its lower contacts establishes a new'holding groundcircuit through the lO-ohm 3 resistor III and over the lower No. 3 backcom tact of the RC relay II! to sleeve conduct-or H2 for holding theestablished connection to the called line and establishes the circuit ofthe reversing (T) relay I08 if the TC relay IIE has been operated fromthe marker, over a circuit which may be traced from battery through thewinding of relay I08, over the right No. 2 back contact of the BY relayI22, over the left No. 1 contacts of the TC relay I I6, over the rightNo. 1 contacts of the CO relay I04 and to ground over the upper contactsof the S relay I32. Relay I00 if it operates reverses the battery andground connection between the windings of the A relay I03 and the tipand ring conductors I05 and I06 of the inter-ofrlce trunk I43 forsupervision at the originating office.

In the preceding discussion, it was assumed that the called line whentested was found to be idle. It will now be assumed that the called linewas found to be busy. Under this condition the OPE relay 257 and the BYrelay 2I8 of the marker areoperated and a circuit is closed overcontacts of such relays, over contacts of the MCA relay 269 and the LVrelay 208 at the trunk link connector 296, for the select magnet 269indicative of the busy condition, a circuit is also established foroperating the select magnet ZB'I indicative of a called line busycondition and a circuit for the RC relay I I! of the trunk circuit isestablished. When, following the operation of relay N7, the hold magnet25I is operated as previously described, the cross point contacts 2Iland 2'59 are operated and a circuit is estab lished from battery throughthe winding of the relay I22 of the trunk circuit, over the BY lead I33, the lower contacts of cross-point contacts 219, the lower contactsof cross-point contacts 2H, conductor I2I and to ground over the lowerNo. 3 contacts of the D relay IIII. Relay I22 thereupon operates andlocks over its left No. 1 contacts to ground on conductor I2I. The RCrelay Ill upon operating locks in a circuit over its upper No. 1contacts, the back contactof ringing trip relay II9, conductor I 20 andthe lower contacts of cross-point contacts 2' to ground on conductor I2I With the BY relay I22 operated, the start (STB) lead I34 from theinterrupter circuit I35 is connected over the left No. 3 back contact ofrelay H6 and the left No. 3 contacts of relay I22 to ground to start theimpulse per minute transmission from the interrupter circuit and the LEIor tone lead I36 is connected over the right No. 2 back contact of relayIIS and the right No. 1 contacts of relay I22 through condenser. E42 andthe left winding of the A relay I93 to ground. Tone current is therebyinduced into the transmission circuit extending over the calling lineloop whereby the calling subscriber hears the busy tone. When line busyflash is required the circuit of the T relay I08 is interrupted at 60impulses per minute. This circuit extends from battery through thewinding of such relay, over the No. 2 right front contact of the BYrelay I22, the left No. 2 back contact of the TC relay H5 and over theLB lead I31 to interrupted ground.

If the marker is unable to complete the. call because an idle channel isnot available, the OFH relay 2H and the OF relay 2I9 of the marker areoperated and cause the operation of select magnets 26!! and 269 and theoperation ofv the RC relay II'I over contacts of the LV relay 200 andMCA relay 209 of the trunk link connector. When, following the operationof the relay II I the hold magnet 25I of the ringing selection switch250 is operated as previously described, the cross-point contacts 210and ZlI are operated and a circuit is established from battery throughthe winding of the relay I22of the trunk circuit over the BY lead I33,the lower contacts of crosspoint contacts 219, the lower contacts ofcrosspoint contacts 210, conductor I2I and to ground over the lower No.3 contacts of the D relay IIO. Relay I22 thereupon operates and looksover its left No. 1 contacts to ground on conductor I2I. The RC relayII'I upon operating locks over a circuit over its upper No. 1 contacts,the back 1.

contact of the ringing trip relay II9, conductor I20 and the lowercontacts of cross-point contacts 213 and to ground on conductor I 2|.Relay I 22 upon operating now establishes a circuit from battery throughthe winding of the TC relay IIii, over the left No. 2 contacts ofrelayI22, conductor I28 and the next to lower contacts of operatedcross-point contacts 210 to ground on the ringing supply ground lead238. Relay IIB now operates and looks over its rightNo. 1 contacts andthe left No. 4 front contact of the BY relay I22 to ground.

With the BY relay I22 and the TC relay H5 both operated, the start (STO)lead I30 to the interrupter circuit I35 is connected over the left No. 3front contact of relay I I6 and the left No. 3 contacts of relay I22 toground to start the 120 impulse per minute transmission from theinterrupter circuit and the overflow tone (OFT) lead I39 is connectedover the right No. 2 front contact of relay I I5 and the right No. 1contacts of relay 522, through condenser I 42 and the left winding ofthe A relay I33 to ground. Tone current is induced into the transmissioncircuit extending over the calling line loop whereby the i callingsubscriber hears the overflow busy tone. When a flashing signal is alsorequired-the circuit of relay I 03 is interrupted at 120 impulses perminute. This circuit extends from battery through the winding of suchrelay, over the No.

Zright front contact of the BY relay I22 and the left No. 2 frontcontact of the TC relay I It to the interrupter OF ground lead I40extending to the interrupter circuit.

If the calling subscriber is first to disconnect,

the trunk loop becomes opened thereby releasing the A relay I03 followedby the release of the D relay IIII. Relay IIB inturn releases theCOrelay i0 3 and the TC relay II6 if previously operated. The T relay I08releases when either the CO relay I04 or the TC relay H5 releases. Withthe CO relay I04 released, the windings of the A relay 533 arereconnected to the conductors I05 and I08 of the incoming trunk circuitI02 in their normal polarity direction, but the trunk loop being open atthis time relay I33 does not operate The D relay I I0 upon releasingopens the transmission path from the windings of the A relay I03 to theincoming trunk circuit and over its called subscriber hangs up torelease the S relay I 32 or the RC relay I I1 operates upon a time-out.

With relay I32 operated and the CO relayIM released, a circuit isestablished from battery through the winding of heater unit I4I over theright No. 1 normal contacts of the CO relay I04 and to ground over theupper contacts of the S relay I32 and after an interval of about fifteenseconds the contacts of the heater unit close to establish a circuitfrom battery through the winding of the RC relay II'I, contacts ofheater unit I II, the left No. 2 back contact of the CO relay I04 and toground over the upper contacts of the S relay I32. Relay II {uponoperating disconnects ground from the sleeve lead I I2 at its lower No.3 back contact thereby releasing the switches on the trunk link frame20I and on the line link frame 2 I2. When the release of such switcheshas taken place and the disconnection of the called subscriber line 200from the trunk circuit has become effective, the S relay I32 releases inturn releasing the heater unit MI and the RC relay I I'I., If the trunkcircuit is reselected during the timed release of the calledsubscriber's line, the A relay I 03 reop'erates causing an incomingregister to be attached to the trunk circuit as previously described.However, whenthe CO relay I04 operates it opens the circuit through thewinding and contacts of "the heater unit I to prevent the operation ofthe RC relay II'I. V

Should the called subscriber disconnect at any time before theoperationof the D relay III], the

, called line will be released at once since with relay I32 releasedandrelayl I I0 unoperated no resistance ground is applied to sleeveconductor I I2 to hold the cross bar switches. After the D relay H3operates and applies resistance ground to sleeve conductor I I2, thecalled line will be released and' the cross bar switches released whenthe marker operates the F relay I I3 of the trunk circuit and therebyoperates relay 203 of the trunk link connector. b

When the called subscriber 200 disconnects first the S relay I 32 upon'releasing releases the T relay I08 to reverse the trunk circuit as asupervisory signal. The connection to thecalled line is then held byresistance ground connected to sleeve conductor II2 by the operated Drelay IIIl until the calling end of the trunk circuit is released eitherby time-out at the distant office or discon nection by the callingsubscriber. The. A relay I03, CO relay I04, and D relay H0 then releaserestoring the trunk circuit to normal.

In' the preceding discussion it was assumed that the ringing currentrequired to ring on the individual line 200-was applicable over thecrosspoint contacts 216 and 213 of the ringing control switch 250 fromthe code 1 generator lead 28l. For calls to two-party lines the markeroperates select magnet 266 to close. cross-point contacts H3 and inaddition operates select magnet 26I to close cross-point contacts 2' ifthe wanted subscriber is a tip party and the, ringing current is to beapplied over the tip conductor of the called line or operates selectmagnet 260 to close crosspoint contacts 210 if the wanted subscriber isa ring party and theringing current is to be applied over the ringconductor of the called line. I

If the called subscriber is a substation of a four-party semiselectivc,a four-p T1111 lective, an eight-party semiselective, or atenpartyfive-code line, and is to be signaled by one long mg' c rnegatwesuperimposed ringing current, the marker will operate to select magnet26.5 to close the cross-point contacts 215 and will, in addition,operate either select magnet 25I or 250 to close either cross-pointcontacts 2H or 21!} dependent upon whether the substation to be calledis to be rung over the tip or ring conductor of the line. With thecross-point contacts 216 closed and cross-point contacts 21I alsoclosed, code ringing is supplied from the ringing supply source 280 overthe code generator lead 28'I, the upper contacts of cross-point contacts216, lead I26, the winding of ringing trip relay I [9, lead I21, thenext to upper contacts of cross-point contacts 21I, conductor I28, the.inner right contacts of the PU relay I24, the upper Nov 4 front contactof the RC relay H1 and over the tip conductor of the establishedconnection to the called line, thence through the ringers on the tipside of the line to ground. With the crosspoint contacts 216 and 210closed, code ringing is supplied from the ringing supply source 2822over the code generator lead 2!", the u er contacts of cross-pointcontacts 216, lead I26, winding of ringing trip relay IIS, lead I21, thenext to upper contacts of cross-point contacts 215), conductor I29, theouter right contacts of PU relay I24, the lower No. 2 front contact ofthe RC relay I I1 and over the ring conductor of the establishedconnection to the called line, thence through the ringers on the ringside of the line to ground. Thus ringing current of the negativesuperimposed type is supplied and the ringing which starts immediatelyafter the pick-up interval determined by the pick-up interrupterconnected to lead I23 is on for two seconds and then off for theremaining four seconds of the ringing interval.

, If the ringing current is applied to the tip of a four-party fullselective line, only they negatively polarized ringer on the tip sidewill respond to call the subscriber at that substation or if applied tothe tip of an eight-party semiselective line onlv the two negativelypolarized ringers connected to the tip side will respond and since thecode is a single long ring, only one of the subscribers thus rung willrecognize it as his ringing code signal. If the ringing current isapplied to the tip of a four-party semiselective line, both ringers onthe tip side will respond, but since the signal is a single long ring,only one of the two tip party subscribers will recognize it as hisringing code signal. If the ringing current is applied to the tip of aten-party fivecode line all five of the ringers on the tip side of theline will respond, but since the signal is a single long ring, only oneof the five subscribers who may hear the ring will recognize it as hisringing code signal.

If the ringing current is applied to the ring of a four-party fullselective line, only the negatively polarized ringer on the ring sidewill respond to call the subscriber at that substation or if applied tothe ring side of an eight-party semiselective line only the twonegatively polarized ringers connected to the ring side will respond andsince the code is a single long ring only one of the subscribers thusrung will reco nize it as his ringing code signal. If the ringingcurrent is'applied to the ring of a four-party semi-selective line bothringers on the ring side will respond, but since the signal is a singlelong ring, only one of the two subscribers thus rung will recognize itas his ringing code signal. If the r nging current is applied to thering 91? ten-party five-code line all five of the ringers on the ringside of the line will respond, but since the signal is a single longring, only one of' the five subscribers who may hear the ring willrecognize it as his ringing code signal.

If the called subscriber is at a substation on a four-party fullselective or eight-party semiselective line and is to be signaled by onelong ring of positive superimposed ringing current, the marker willoperate the select magnet 261 to close the cross-point contacts 211 andwill, in addition, operate either select magnet 26! or 260 to closeeither cross-point contacts 21! or 210 dependent upon whether thesubscriber to be called is to be. rung over the tip or over the ringconductor of the line. With the cross-point contacts 211 closed ringingcurrent from the ringing supply 28!! is applied over the code +1generator lead 282, over the upper contacts of cross-point contacts 211and thence as traced to either the tip or ring conductor of the calledline dependent upon whether the tip cross-point contacts 2' or the ringcross-point contacts 210 have been closed. Ringing current in this caseis positive superimposed and is supplied for two seconds followed by afour-second silent inter val. If the ringing current is applied to thetip of a four-party full selective line, only the positively polarizedringer on the tip side of the line will respond to call the subscriberat that substation or if applied to the ring of such line only thepositively polarized ringer on the ring side of the line will respond tocall the subscriber at that substation. If the ringing current isapplied to the tip of an eight-party semiselective line only the twopositively polarized ringers on the tip side of the line will respond,but since the code is a single long ring, only one of the subscribersthus rung will recognize it as his ringing code signal or, if theringing current is applied to the ring of such line only the twopositively polarized ringers on the ring side of the line will respond,but since the code is a single long ring, only one of the subscribersthus rung will recognize it as his ringing code signal.

If the called subscriber is at a substation on a four-partysemiselective line, on an eight-party semiselective line, or on aten-party five-code line, and is to be signaled by two short rings ofnegative superimposed ringing current, the marker will operate theselect magnet 262 to close the cross-point contacts 212 and will, inaddition, operate either select magnet 26! or 260 to close eithercross-point contacts 21I or 2152 dependent upon whether the substationto be called is to be rung over the tip or over the ring conductor ofthe line. With the cross-point contacts 212 closed, ringing current fromthe ringing supply 280 is applied over the code 2 generator lead 283,over the upper contacts of cross-point contacts 212 and thence as tracedto either the tip or ring conductor of the called line dependent uponwhether the tip cross-point contacts 21i or the ring cross-pointcontacts 210 have been closed. Ringing current in this case is negativesuperimposed and is supplied for one second, off for one second, onagain for one second and oii for the remaining three seconds of theringing interval, and thus a two short ring code is supplied. If theringing current is applied to the tip of a four-party semiselectiveline, the two ringers connected to the tip of the line will respond, butsince the ringing code is two short;

rings, only one of the two subscribers thus rung will recognize it ashis ringing code signal. If

the current is applied to the ring of such line the two ringersconnected to the ring of the line will respond, but since the ringingcode is two short rings, only one of the two subscribers thus rung willrecognize it as his ringing code signal. If the current is applied tothe tip of an eightparty semiselective line, the two negativelypolarized ringers on the tip side will respond, but since the ringingcode is two short rings, only one of the two subscribers thus rung willrecognize it as his ringing code signal, or, if the current is appliedto the ring of such line the two negatively polarized ringers on thering side will respond, but since the ringing code is two short only oneof the two subscribers thus rung will recognize it as his ringing codesignal. If the ringing current is applied to the tip of a ten-partyfive-code line all of the ringers on the tip side of the line willrespond but only one of the five subscribers thus rung will recognizethe ring as his ringing code signal, or if the ringing current isapplied to the ring of such line, all of the ringers on the ring side ofthe line will respond but only one of the five subscribers thus rungwill recognize the ring as his ringing code sighal.

If the called subscriber is on an eight-party semiselective line and isto be signaled by two short rings of positive superimposed ringingcurrent, the marker will operate the select magnet 268 to close thecross-point contacts 218 and in addition will operate either selectmagnet 25! or 260 to close either cross-point contacts ill or 210dependent upon whether the substation to be called is to be rung overthe tip or over the ring conductor of the line. With the cross-pointcontacts 218 closed, ringing current from the ringing supply 28!] isapplied over the code 2+ lead 284, over the upper contacts or"cross-point contacts 218 and thence as traced to either the tip or ringconductor of the called line dependent upon whether the tip cross-pointcontacts Eli or the ring cross-point contacts Zlil have been closed.Ringing current in this case is positive superimposed and is suppliedfor one second, oil" for one second, on again for one second and oil forthe remaining three seconds of the ringing interval, and thus atwo-short ring code is supplied. If the ringing current is applied tothe tip side of the line the two positively polarised ringers connectedto the tip side of the line will respond, but since the ringing code istwo short rings, only one of the two subscribers thus rung willrecognize it as his ringing code signal, or if the current is applied tothe ring side of the line then the two positively polarized ringersconnected to the ring side of the line will respond, but since theringing code is two short rings, only one of the two subscribers thusrung will recognize it as his ringing code signal.

If the called subscriber is on a ten-party fivecode line, the markerwill operate either the select magnet 253, 264 or 265 to cause theclosure of either the cross-point contacts 213, 214 or 215, dependentupon whether the party to be called has a ringing code of one longfollowed by one short ring, a code of one long followed by two shortrings, or a code of one long ring followed by one short ring and asecond long ring. In addition, the marker will cause the closure of thetip cross-point contacts 2' or the ring cross-point contacts 210 throughthe operation of select magnet 26| or 260 dependent upon whether thecalled subscriber. is at a .tip

or ring substation. If the called subscriber is to be signaled with aringing code of one long ring followed by a. single short ring, theclosure of cross-point contacts 213 establishes a ringing circuit fromthe ringin supply 280 over the code 3 generator lead 285, over the uppercontacts of cross-point contacts 213, thence as traced to the tip orring conductor of the called line dependent upon whether the tipcross-point contacts 21! or the ring cross-point contacts 210 have beenclosed. Ringing current in this case is negative superimposed and isapplied for one and one-half seconds, off for one-half sec- 0nd, on forone-half second and oil for the remaining three and one-half seconds ofthe rings ing interval. If the ringing current is applied to the tipside of the line, the five ringers on the tip side will respond, butonly one of the subscribers thus rung will recognize the ring as hisringing code signal, or if the ringing current is applied to the ringside of the line, the five ringers on the ring side will respond, butonly one of the subscribers thus rung will recognize the ring as hisringing code signal. It the called subscriber is to be signaled with aringing code of one long followed by two short rings, the 010- sure ofcross-point contacts 214 establishes a ringing circuit from the ringingsupply 280, over the code 4 generator lead 286, over the upper contactsof cross-point contacts 214, thence as traced to the tip or ringconductor of the called line dependent upon whether the tip cross-pointcontacts 21! or the ring cross-point contacts 21!] have been closed.Ringing current in this case is negative superimposed and is applied forone and one-half seconds, off for one-half second, on for one' halfsecond, on another half second and off for the remaining two andone-half sec.- uncle of the rin ing interval. If the ringing current isapplied to the tip side of the line, the five ringers on the tip sidewill respond but only one of the subscribers thus rung will recognizethe ring as his ringing code signal, or if the'ringing current isapplied to the ring side of the line, the five ringers on the ringsidewill respond but only one of the subscribers thus rung will recognizethe ring as his ringing signal. If the called substation is to besignaled with a ringing code of one long, one short and another longring, the closure of cross-point contacts 2'75 establishes a ringingcircuit from the ringing supply 280 over the code 5 generator lead 281,over the upper contacts of cross-point contacts 275, thence as traced tothe tip or ring conductor of the called line, dependent :upon whetherthe tip cross-point contacts 2'H or the ring cross-point contacts 210have been closed. Ringing current in this case is negative superimposedand is applied for one and one-half seconds, 011 one-half second, onone-half second, off one-half second, on one and one-half seconds andoff for the remaining one and one half seconds of the ringing interval.If the ringing current is supplied to the tip side of the line, the fiveringers on the tip side will respond but only one of the subscribersthus rung will recognize the ring as his ringing code signal, or if theringing current is applied to the ring side of the line, the fiveringers on the ring side will respond but only one of the subscribersthus rung will recognize the ring as his ringing signal.

- To recapitulate, the selection of ringing cur rentfor ringing anysubscriber on a'ny'oneof they types of lines above discussed. is inaccordance with the following table:

Ringing selection table Code Ringing Impulses Marker Select Polar- 7,

Relay Magnet it 1 41 2 1 y 8 1 p sclcc- Sclecselcctive tivc tive Modenor ROT

no'r12 H RCT nor aunt 671 u nor RCT14 RCT 2m HOT 15.

RCT 270 a What is claimed is:

1. In a telephone system, a trunk circuit, a common control. means. forcontrolling the establishment of a telephone connection including saidtrunk circuit, a cross bar switch comprising a plurality of cross-pointcontact sets, a plurality of sources of ringing current connected tosaid contact sets, means under the control of said common control meansto prepare a plurality of said contact sets to select one of saidsources of ringing current, and means under the joint control of saidcommon control means and said trunk circuit to close said preparedcontact sets to connect said selected source of ringing current to saidtrunk circuit.

2. In a telephone system, a plurality of trunk circuits, a commoncontrol means for controlling the establishment of a telephoneconnection including any one of said trunk circuits, a plurality ofsources of ringing current, a cross bar switch comprising a plurality ofcoordinately arranged cross-point contact sets, the contact sets in theseveral rows in one coordinate direction being connected to said trunkcircuits respectively and the contact sets in the several rows in theother coordinate direction being connected to said sources of ringingcurrent, respectively, means under the control of said common controlmeans to prepare a plurality of said contact sets to select one of saidsources of ringing current, and means under the joint control of saidcommon control means and said selected trunk circuit to close saidprepared contact sets to connect said selected source of ringing currentto said trunk circuit.

3. In a telephone system, a plurality of trunk circuits, at commoncontrol means for controlling the stablishment of a telephone connectionincluding any one of said trunk circuits, a pluralityof sources ofringing current, across bar switch comprising a; plurality ofcoordinately arranged cross-point contact sets, the contact sets in theseveral rows in one coordinate direction being connected to said trunkcircuits respectively and the contact sets in the other coordinatedirection being connected to said sources of ringing. current,respectively, select magnets operable under the control of said commoncontrol means to prepare a plurality of said contact sets to select oneof said sources of ringing current, and a hold magnet under the jointcontrol of said common control means and said selected trunk circuit toclose said prepared contact sets to connect said selected source ofringing current to said trunk circuit.

4. In a telephone system, a trunk circuit having a tip and a ringconductor, a common control means for controlling the establishment of atelephone connection including said trunk circuit, a cross bar switchcomprising a plurality of cross-point contact sets, a plurality ofsources of ringing current connected to certain of said contact sets,the tip and ring conductors of said trunk circuits being connected toothers of said contact sets, means under the control of said commoncontrol means to prepare one of said certain contact sets to select oneof said sources of ringing current and to prepare one of said lattercontact sets to determine the application of the selected ringingcurrent to either the tip or ring conductor of said trunk circuit, andmeans under the joint control of said common control means and saidtrunk circuit to close said prepared contact sets to connect saidselected source of ringing current to the tip or ring conductor of saidtrunk circuit. a

5. In a telephone system, a plurality of trunk circuits each having atip and a ring conductor, a common control means for controlling theestablishment of a telephone connection including any one of said trunkcircuits, a plurality of sources of ringing current, a cross bar switchcomprising a plurality of coordinately arranged cross-point contactsets, the contact sets in the several rows in one coordinate directionbeing connected to said trunk circuits respectively, the contact sets incertain rows in the other coordinate direction being connected to saidsources of ringing current respectively and the contact sets in otherrows in the latter coordinate direction being connected to determine theapplica-: tion of any selected ringing current source .to either the tipor ring conductor of any one of said trunk circuits, means under thecontrol of said common control means to prepare a contact set in one ofsaid certain rows and a contact set in one of said latter rows to selectone of said sources of ringing current and to determine the applicationthereof to either the tip or ring conductor of any of said trunkcircuits, and means under the joint control of said common control meansand. a selected trunk circuit to close said prepared contact sets toconnect said selected source of ringing current to the tip or ringconductor of said selected trunk circuit. 1

6. In a telephone system, a trunk circuit, a common control means forcontrolling the estab lishment of a telephone connection including saidtrunk circuit, a cross bar switch comprising a plurality of cross-pointcontact sets, a plurality. of sourcesof ringing current associated withsaid: contact sets, certain of which sources are. of the: code ringingtype, means under the controlzxot said common control means to'prepare'a plurality" of, said contact sets to select one of said sources of.ringing current,rmeans.. underithesjoint".- control 17 of said commoncontrol means and said trunk circuit to close said prepared contactsets, a pickup relay in said trunk circuit for applying selected ringingcurrent to said trunk circuit, a ringing interrupter effective to causethe operation of said relay at the beginning of a ringing code cyclewhere ringing current of the code ringing type is selected forapplication to said trunk circuit, and means controlled over a closedcross-point contact set of said switch to operate said relay independentof said interrupter when a ringing current source of the one-ring typeis selected for application to said trunk circuit.

7. In a telephone system, a trunk circuit having a tip and a ringconductor, a common control means for controlling the establishment of atelephone connection including said trunk circuit, a cross bar switchcomprising a plurality of crosspoint contact sets, a plurality ofsources of ringing current associated with certain of said contact sets,certain of which sources are of the code ringing type, the tip and ringconductors of said trunk circuit being associated with others of saidcontact sets, means under the control of said common control means toprepare one of said certain contact sets to select one of said sourcesofringing current and one of said latter contact sets to determine theapplication thereof to either the tip or ring conductor of said trunkcircuit, means under the joint control of said common control means andsaid trunk circuit to close said prepared contact sets, a pick-up relayin said trunk circuit for applying selected ringing current to saidtrunk circuit, a ringing interrupter efiective to cause the operation ofsaid relay. at the beginning of a ringing code cycle when ringingcurrent of the code ringing type is selected for application to saidtrunk circuit, and means controlled over a cross-point contact setclosedto select a ringin current source of the one-ring type to operatesaid relay independent of said interrupter to cause the immediateapplication of ringing current to said trunk circuit.

8. In a telephone system, a called line, a trunk circuit, a commoncontrol means for controlling the establishment of a telephoneconnection to said called line including said trunk circuit, a cross barswitch comprising a plurality of crosspoint contact sets, a plurality ofsources of ringing current associated with certain of said contact sets,a source of busy tone current, a relay in said trunk circuit forapplying current from said sources to said trunk circuit, a circuit forsaid relay controllable over another of said crosspoint contact sets,means in said common control means for determining the idle or busycondition of said called line, means underjthe control of said commoncontrol means to prepare a plurality of said certain contact sets'toselect one of said sources of ringing current if said line is found tobe idle and to prepare said other contact set if said line is found tobe busy, and means under the joint control of said common control meansand said trunk circuit to close said prepared contact sets to connectsaid selected source of ringing current or said source of busy tonecurrent to said trunk circuit.

9. In a telephone system, a called line, a plurality of trunk circuitseach having a tip and a ring conductor, switching means, a commoncontrol means for controlling said switching means to establish atelephone connection to said called line including any one of said trunkcircuits, a source of busy tone current, sources of ringing current, arelay in each trunk circuit for applying current from said source toconductors of said trunk circuit, a cross bar switch comprising aplurality of coordinately arranged cross-point contact sets, the contactsets in the several rows in one coordinate direction being allocated tosaid trunk circuits respectively, the contact sets in certain rows inthe other coordinate direction being allocated to the selection of saidsources of ringing current respectively, the contact sets in two otherrows in the latter coordinate direction being allocated to determine theapplication of any selected ringing current source to either the tip orring conductor of any one of said trunk circuits and a further row inthe latter coordinate direction being allocated to the operation of thebusy relay of any one Of said trunk circuits, means in said commoncontrol means for determining the idle or busy condition of said calledline, means under the control of said common control means to prepare acontact set in said certain rows and a contact set in one of said tworows to select one of said sources of ringing current if said calledline is found to be idle or to prepare a contact set in said further rowand a contact set in one of said two rows to operate the busy relay of aselected trunk circuit if said called line is found to be busy, andmeans under the joint control of said common control means and saidselected trunk circuit to close said prepared contact sets to connectsaid selected source of ringing current or said source of busy tonecurrent to said selected trunk circuit.

MYRON C. GODDARD.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,120,419 Stokely June 14, 19382,430,316 Voss Nov. 4, 1947

